i have an 87 iroc that i purchased about a year ago. sometimes it fires right up and sometimes it will just crank (no spark). i have checked and it does get power to the coil (the bigger pink wire that plugs into the coil). but the coil does not put out anything. the coil is new.. so is the cap and rotor. i was wondering if you guys think its a problem with the coil?? or for some other reason the coil isn't getting the message to fire.. ecm maybe?? any ideas on what i should be checking?? PLEASE HELP!

 

Not sure if this will help, but this problem sounds similar to the one in the below article.

1986 chevy starting issue